MOS differential voltage-to-current converter circuit with improved linearity

Abstract

A MOS differential voltage-to-current converter circuit has first and second MOS transistors forming a differential pair and a resistor connected between the sources of the first and second MOS transistors. These first and second MOS transistors are connected to the sources of third and fourth MOS transistors, at respective sources. By biasing the third and fourth MOS transistors, with a constant current, differential input voltage is supplied to the gates of the third and fourth MOS transistors. The drain outputs of the third and fourth MOS transistors are respectively connected to first and second signal transmission circuits for transmitting the drain outputs to the gates of the first and second MOS transistors through the first and second signal transmission circuits. With taking the current flowing through the first and second MOS transistors as differential output, a voltage-to-current conversion characteristics not depending upon variable property of the MOS transistors can be obtained.

What is claimed is: 
     
       1. A MOS differential voltage-to-current converter circuit comprising: first and second MOS transistors;   a resistor connected between the sources of said first and second MOS transistors;   a first constant current source for supplying operation current for said first and second MOS transistors;   third and fourth MOS transistors having sources respectively connected to the source of said first and second MOS transistors and receiving a differential input voltage at the gates thereof;   second and third constant current sources for supplying operation currents for said third and fourth MOS transistors, respectively, said second and third constant current sources being connected to the drains of said third and fourth MOS transistors, respectively; and   first and second signal transmission means for transmitting drain outputs of said third and fourth MOS transistors to the gates of said first and second MOS transistors for taking the current flowing through said first and second MOS transistors as a differential output, wherein said first and second signal transmission means include one of an amplifier circuit, an attenuation circuit, and a voltage follower circuit.   
     
     
       2. A MOS differential voltage-to-current converter circuit comprising: first and second MOS transistors;   a resistor connected between the drains of said first and second MOS transistors;   a first constant current source for supplying operation current for said first and second MOS transistors;   third and fourth MOS transistors having sources respectively connected to the drain of said first and second MOS transistors and receiving a differential input voltage at the gates thereof;   second and third constant current sources for supplying operation currents for said third and fourth MOS transistors, respectively, said second and third constant current sources being connected to the drains of said third and fourth MOS transistors, respectively; and   first and second signal transmission means for transmitting brain outputs of said third and fourth MOS transistors to the gates of said first and second MOS transistors for taking the current flowing through said first and second MOS transistors as a differential output, wherein said first and second signal transmission means include one of an amplifier circuit, an attenuation circuit, and a voltage follower circuit.